Las- willan



UNITED STATES- PATENT OFFIC JOHN HADDEN DOUGLAS-WILLAN AND FRANK EUSTAOE WELKINS BOWEN,

I OF LONDON, ENGLAND.

FILAMENT FOR ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 577,499, dated February 23, 1897. Application filed August 3, 1896. Serial No. 601,532. (No specimens.)

To all whom it may concern.-

Be it known that we, JOHN HADDEN DOUG- LAS-WILLAN, residing at 16 St. Helens Place, and FRANK EUSTACE WELKINS BOWEN, of Selwood, Mount Avenue, Ealing, London, England, subjects of the Queen of Great Brit ain, have invented certain new and useful Improvements in Processes of Making Filaments for Electric Lamps, of which the following is a specification.

This invention relates to a method of treating or flashing carbon or compound filaments whereby they are rendered capable of being worked at high temperatures without the rapid disintegration which would obtain in the case of filaments treated With hydrocarbons alone. In order to effect this, we

Among such compounds suitable for the purpose we may mention the borates of the alcoholssuch as B(OOH and (O H BO In order to lower the vaporizing-point of these substances, we preferably add from one to two per cent. of ethyl iodid.

What we claim is 1. The process of treating filaments consist- 

